Yslow is a Firefox addon, I suggest downloading it. It gives you all sorts of cool stats on how your website is performing. Such as, an overall Grade and score, and most importantly, the number of http requests and the total weight of your page.
After downloading Yslow, here was the stats of my home page (http://www.jc-designs.net):
Then, I downloaded something called Minify, which you can get here. It is a php script that combines all your css files into one, and all your js files into one. The directions are pretty easy.
Once you have downloaded it, put it on your server in the root directory, and open this url: http://yoursite.com/min/builder/.
You then add all of your css files, in the order you have them in. Be careful here…if you have any @import in your main css file, it will screw it up. Trust me, I found this out before I actually read the line that tells you that. Once you have all the files listed, click on update. It then gives you the html to use to replace the linked css files. Plus a line to add to one of the minifier config files. I know, sounds scary, but on that build page, it tells you exactly what to do. Then you do the same for the js files.
What does all that crap get you? Read on!